Thermal relay



F. WELLS 2689288 Sept. 14, 1954 THERMAL RELAY Filed Dee. l, 1951 Egl-Patented Sept. 14, 1954 THERMAL RELAYV Erank; Wells, East Paterson, N.J., assignor to, Eureka. Television and Tube; Corporation, Haw-- thorne;N. J., a, corporation of NcwJersey ApplicationDecember 1, 1951-, SerialNo.4 259,415

This invention relates to: thermal relays,l and more specificallyV thoseof, the snap. action, time delay-type;`

Bresently: known. thermal: relays are subject to; an, objectionablechattering upon; makingl and; breaking Contact.; This chattering is. dueto; the gradual: motion.` ofy the thermalA actuatingv arm,. which. isusuallyr in,` the form of` a: bi-metallic; strip surrounded oradjacenttoa. heatingI ele. ment... Othery objections. to` presentlyknownre.- lays areit'hati they. do. not produce a positive act;- ing: Contacton: opening; and closing the circuit., Bresently known relays are largeandi subject to,A infjuryfromvibration and;shoclr.V

Accordingly, it. is any object of the present invention to provide a.thermal: relay having a snap; acting contact `on open-ingand; closing,wherein(l a positive actonzwill? be providedv Another object of thepresentinvention is to provide a relay whicn will; be free, of chatter:

upon making andfbreaking of,I thecontact;

Ag further object: of the presentihverrtion is to make a thermalv relayhavingsufliciengtlyy smalt size sa as. to rendery itfree; from damage.from; vibrationandislroclr.

A; feature, of vthe present invent-ion` is` its sealed?l construction@whereby all, of the elements arey pontainedwifthina,glassenvelope;

Another: fea-tureoii the presenti-nverrtion .ie: the provision of: aknown quant-itv-'ofresist roe; wiresy and; the control o1?-L the amountor arr inertses.: within the envelope; t provideraocuracyz AnotherIfeature ofthe present invention is; the. snap-acting hat:spring,employed as` a; switollingdeviceV o A, further feature of.- the.`present; invention is.y the use. oi. a compensating birinetal,whichpre-Yvents ambient... temperatures from affecting the timing device. i

The. invention consistsA of the. construction, combination and,arrangement of. parts, as herein, illustrated. described. and claimed.

In the accompanying drawings, forming a, partV hereof, is illustratedone form of embodiment of the invention, in which drawings similar` reference characters designate correspondingpar-ts, and in which:

Figure I is a view in side elevation, showing a complete` embodiment ofthey present invention.

Figure 2, is avertical section, taken` on line 2.2 inFigure l, lookingin,V the directionot the arrows..

Figure 3.. is a view in perspective, showing the construction of theilat spring and yoke assemlil-v,` in,A accordance with the presentinvention..

Referring to the drawings, Ill indicates,` a: base of glass, dielectricmaterial, or the like, bearing therein contact plugs I-I, tothe inneredge off which arev soldered, as indicatedl at I-2', suitable leads` 3l,32a The leads 31|, 32 are suiciently strong to. support thereon anL.-shaped dielectric block I4. The horizontal arm of: the L-shapediblockv lit supports thereon a biemetallic strip. I5, hereinaftervreferred to as the "acting bil-metal. The` acting loi-metal' |15- is ofconventional construction, but supports at theV freeend thereof artimehdjListing screw member IIB, The screw member I6` is threaded;through the strip If5, so4 that it may be. located`= asdesired duringthetimingy of theidev-icc.

A heater coilf I-f'li surrounds the` acting Ici-metaly t5; and' iselectrically insulated therefrom byr mica strips I-8. The heater coil I1isconnected totwooff the leads II as indicatedi at L9, for the pur-Vpose of supplyingk tol said heater coil` I"I the en; ergizing.electrical potential` A second: iii-metallic strip 20 is: secured to.the verticalaarm. 2l of the4 dielectric block- I4'. The secondloi-metallic strip 21H.; which is: securedi atv one end 225, supports:on its: free endA a. yoke 23. Ther yoke 23; is. suhstantiallyvll-shaped, andi curves back upon ith. self in the direction oi`= the.dielectric L-shaped block I; A flat spr-ingmember 2'4i isv secured atthe ehdi of-'t-he yoke 23; which extendsin the di.l rection of' the baseIll. The.flatispring meinber- Zil'. is: constructed so. as, tov provideav snap. alzatienv when pressure is applied; to the.y central' meme.-ber l thereof. The central` member 26;' is, sub-I stantially= straightand is ilanked; @neither side by* bowed members` 27:.

'Bhe nressureto the central; member Gris are plied by the screw Itcarried by:i the; biemetallio Strip: '15,- Theadiutment the position of.the screw member le, with respect to. the VSerine member 24,v comprisesone of the;,factors-in ad. justingthe time` required for the closingoropening of therelay.

l The free end of the springfmemher 24, islpro.y videdY with. a @Ontaot2,8. Open and'` closed con-k tacts, '-9 3,9, are4 provided on. the endof; leads 3.-I, respectively, whichA in. turn are secured to. Suitable:conta'ct. plugs` carried by the base. It will be-V seen byV theF dottedlines in Fig. 2: that when. the snap acting hat spr-ingY member 2.4: isdepressed, it will jump.. from the closed contact to, the open Contact2.9,- with an almost instantaneous action. When pressure is. relieved.from. the spring 24,. asV by. the cooling of the: birmetallic. Strip I5,the contact 28 carried by.- the end of said, spring will snapback toitsorig. in al positionagainstthe closed contact 30 which is shown inf.u,l1..1ines.inl'ieure2.`

From the foregoing itr` will be seen that the application of electrical-potential to the heater coil I1 will in turn warm the bi-metallic stripl5, so as to cause it to bend. The bending action of the loi-metallicstrip I5 will force the screw member I6 against the central portion 26of the spring 24. The spring 24 will thus be activated with the desiredsnap action. When the electrical potential is removed from the heatingcoil l1, the bi-metallic strip will regain its original position, andrelease the flat spring 24. i

Upon the release of pressure, the flat spring 24 will jump back toassume its original position, wherein the contact 28 bears against theclosed contact 30 adjacent the heater coil l1.

The compensating second bimetal 20, upon which the flat spring 24 iscarried, is essential to the accurate operation of the relay. Thissecond bimetal removes inaccuracies which result in presently knownrelays, and which are brought about by ambient temperatures, which maybe the result of adjacent electronic apparatus or room temperature. Itwill be seen that the bimetal 20 will move forward or away from thebimetal l5, depending upon the changes in ambient temperatures.

The entire actuating portion of the relay described above, is enclosedin a glass envelope 33,

which is sealed to the base I0, and thereafter evacuated. Following theevacuation of the envelope 33, a suitable amount of inert gas isintroduced within said envelope, which inert gas forms another of thefactors whereby the time delay can be controlled. Other factors having abearing upon the time delay interval in the present construction are theamount of resistance wire used to heat the bimetal; the spacing betweenthe adjusting screw I6 and the spring member 24; and the construction ofthe spring itself.

It has been found that to insure the successful operation and long lifeof the present device, the spring member 24 must be constructed of amaterial that will withstand the high temperatures attained by sealingthe relay within the envelope. Metals such as covenium have been foundto be satisfactory for this purpose.

It will be seen from the foregoing that a time delay relay mechanism,having the advantage of snap action, has been provided. The snap actingrelay, furthermore, is capable of being constructed with a minimumamount of size, and with amaximum amount of durability.

It is further possible to very accurately adjust the timing interval inthis device, and to maintain said interval, despite various conditionsunder which the relay may be used.

Having thus fully described the invention,`

what is claimed as new and desired to be secured by Letters Patent ofthe United States, is:

1. A contact switch comprising, a dielectric block, opposed, fixedelectrical contacts supported by said block, an elongated bi-metal stripsecured to the block and extending therefrom, a heating element adjacentthe said bi-metal strip, a support bracket secured to the block inspaced relationship to the bi-metallic member and parallel thereto, asubstantially U shaped yoke secured at one leg to the free end of thesupport bracket having its opposite end extending in the direction ofthe block, a unitary snap spring member formed of fiat spring materialand having a substantially straight central leaf and a bowed leaf memberlaterally disposed on each side of the central leaf, said leaves beingsecured at their free ends to the yoke so as to depend therefrom and liebetween the support bracket and the bi-metal member, a movableelectrical contact member secured to the free end of the snap spring andpositioned so as to alternately connect with one of the opposed fixedcontacts in response to the movement of the snap spring. and a springactuating arm carried by the free end of the bi-metal in contact withthe central spring leaf at all times to transmit the motion of thebi-metal to the spring leaves.

2. A control switch comprising, a dielectric block, opposed fixedelectrical contacts supported A by said block, a first elongatedbi-metal strip secured to the block and extending therefrom, a heatingelement adjacent the said rst bi-metal strip, a support bracketconsisting of a second bimetal secured to the block in spacedrelationship to the bi-metallic member and parallel thereto, asubstantially U shaped yoke secured at one leg to the free end of thesecond bi-metal support bracket having its opposite end extending in thedirection of the block, a unitary snap spring member formed of natspring material and having a substantially straight central leaf and abowed leaf member laterally disposed on each side of the central leaf,said leaves being secured at free ends to the yoke so as to dependtherefrom and lie between the support bracket and the flrst bi-metalmember, a movable electrical contact member secured to the free end ofthe snap spring and positioned so as to alternately connect with one ofthe opposed fixed contacts in response to the movement of the snapspring, and a spring actuating arm carried by the free end of thebi-metal in contact with the central spring leaf at all times totransmit the motion of the bi-metal to the spring leaves.

3. A contact switch comprising, a dielectric block, opposed fixedelectrical contacts supported by said block, an elongated bi-metal stripsecured to the block and extending therefrom, a heating element adjacentthe said bi-metal strip, a support bracket secured to the block inspaced relationship to the bi-metallic member and parallel thereto, asubstantially U shaped yoke secured at one leg to the free end of thesupport bracket having its opposite end extending in the direction ofthe block, a unitary snap spring member4 formed of flat spring materialand having a substantially straight central leaf and a bowed leaf memberlaterally disposed on each side ofthe` central leaf, said leaves beingsecured at their free ends to the yoke so as to depend therefromy andlie between the support bracket and the bi-v metal member, a movableelectrical contact mem ber secured to the free end of the snap springand positioned so as to alternately connect with one of the opposedflxed contacts in response to the movement oi' the snap spring and anaxially` adjustable spring actuating arm carried by the free end ofthem-metal in contact with theV central spring leaf at all times toadjustabl'y` transmit the motion of the bi-,metal to the spring leaves.

References cited m the fue of this patent UNITED STATES PATENTS NumberName Date 1,571,104 Baker Jan. 26, 1926 2,484,112 Moorhead Oct. l1, 19492,489,391 Thompson Nov. 29, 1949 2,494,863 Dietz Jan. 17, 1950 2,564,321Brosseau Aug. 14, 1951 2,568,323 Dales Sept. 18, 1951 2,658,975Zuckerman Nov. 10, 1953

